The present invention relates to an X-ray cassette for X-ray sensitive sheet-like material, preferably for a film coated with a stimulable phosphor layer and a method of processing such a cassette.
A cassette of the foregoing type has been disclosed, for example in EP No. 0,079,557 B1 while a method of handling such a cassette by means of devices available on the market has been disclosed in EP No. 0,142,709 A2.
The known cassette with a photographic material is distinguished by that the photographic material has an identification means which are rigidly attached to that material. Furthermore, such a cassette has an opening which is made in conformity with the identification means so that the identification of the cassette is possible from its outer side. Thereby the identification means can be formed by a magnetic indication medium on which or by which identification data can be magnetically indicated or scanned. The advantage of such a cassette resides in that identification data are applied directly on the photographic material non-separately from it and thus can not be lost, and yet these identification data can be applied from outside or scanned. Suitable methods and devices for using such a cassette with the phosphorus-coated film are substantially such that, upon the exposure of the film positioned in the cassette with X-rays a latent image is produced. The latent image is brought to luminescence in the reading station after being removed from the cassette by means of a laser scanner (the phosphorus is stimulated) and the latent image is converted into digital electric image signals which can be converted into a visible image on the screen or image screen receiving apparatus or a computer-controlled laser beam receiving apparatus. Then the remaining image is erased and the film is returned into the cassette-leading apparatus. The identification data on the identification means of the film should be thereby read-out by a suitable reading apparatus and converted into digital electric identification signals and added to the aforementioned digital image signals. On the other hand, after erasing of the latent image from the film the image signals are useless. The cassettes which are transported from the reading station separately from the films have no identification means or data which can be used for re-loading of the cassettes in the re-loading apparatus.
The disadvantage of such known X-ray cassettes having films with the layer of the stimulable phosphor resides in that the cassette must have a non-closable window for identification means located on the film side. If an incorrect film is inserted it becomes exposed at the location of the window which would result in an "erased" film which can not be used for receiving the image, or the identification means can not be read out if they are positioned on the side of the film, which faces away from the phosphorus layer. Furthermore, the manufacture of the cassette with a window is more expensive than the cassette that has no opening. Further, despite the window in the cassette the reading device for the identification means should be provided in the reading station because otherwise digital image signals and identification signals can not be combined and the data on the film would not be useful anyway. The disadvantage of the known method resides in that the film between being removed from the cassette in the reading station and the reinsertion into the cassette in the cassette-loading apparatus is not protected against mechanical influence so that the phosphor layer can be subject to wear and/or damage.